Bat is flying 5m/s while chasing an insect that is flying in the same direction. The bat emits 40kHz chirp and hears a 40.4kHz reflected sound wave. What is the speed of the insect?

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1 answer

The reflected sound has a higher frequency, so the insect is approaching.

(delta f)/f = 0.4/40 = 0.01 = 2 V/a

The number 2 accounts for Doppler shift incident and reflected sound

a is the sound speed. Assume a = 340 m/s

V = 1.7 m/s